A person becomes prudent by learning to distinguish what is essential from what is non essential, to set the right goals and to choose the best means of attaining them. 

The virtue of prudence directs all the other virtues. For prudence is the ability to recognize what is right. After all, someone who wants to lead a good life must know what the “good” is and recognize its worth. Like the merchant in the Gospel “who, on finding one pearl of great value, went and sold all that he had and bought it” (Mt 13:46). Only a prudent person can apply the virtues of justice, fortitude, and moderation so as to do good.

A sin is a word, deed, or intention by which man deliberately and voluntarily offends against the true order of things, as God’s loving providence has arranged them.

To sin means more than to violate some rules about which men have agreed. Sin turns freely and deliberately against God’s love and ignores him. Sin is ultimately “love of oneself even to contempt of God” (St. Augustine), and in the extreme case the sinful creature says, “I want to be like God” (see Gen 3:5). Just as sin burdens me with guilt, wounds me, and by its consequences ruins me, so too it poisons and damages the world in which I live. It becomes possible to recognize sin and its seriousness by drawing near to God. 

The Fifth Commandment forbids also the use of violence against one’s own body. Jesus expressly demands that we accept and love ourselves: “You shall love your neighbor as yourself” (Mt 22:39).

Self-destructive acts against one’s own body (“body piercings”, cutting and so on) are in most cases psychological reactions to experiences of abandonment and a lack of love; hence they call first and foremost for our sincere and loving response. Within the context of organ donation, it must be made clear, however, that there is no human right to destroy one’s own God-given body.

Because she would like to protect love. A person can give someone else no greater gift than himself. “I love you” means for both: “I want only you, I want all that you are, and I want to
give myself to you forever!” Because that is so, we cannot, even with our bodies, really say “I love you” temporarily or on a trial basis. 

Many people take their premarital relationships seriously. And yet there are two reservations involved that are incompatible with love: the “exit option” and the fear of a child. Because love is so great, so sacred, and so unique, the Church teaches young people the obligation to wait until they are married before they start to have sexual relations.

Fornication (from Greek porneia) originally meant pagan sexual practice, for instance, temple prostitution. Later the term was applied to all forms of sexual activity outside of  marriage. Today in English it generally refers to consensual sexual relations between an unmarried man and an unmarried woman.

Fornication is often based on seduction, lies, violence, dependency, and abuse. Fornication is therefore a serious offense against charity; it harms the dignity of the person and fails to recognize the meaning of human sexuality. Civil authorities have the duty to protect minors especially from fornication.

According to God’s will, husband and wife should encounter each other in bodily union so as to be united ever more deeply with one another in love and to allow children to proceed from their love.

In Christianity, the body, pleasure, and erotic joy enjoy a high status: “Christianity . .  believes that matter is good, that God Himself once took on a human body, that some kind of body is going to be given to us even in Heaven and is going to be an essential part of our happiness, our beauty and our energy. Christianity has glorified marriage more than any other religion: and nearly all the greatest love poetry in the world has been produced by Christians. If anyone says that sex, in itself, is bad, Christianity contradicts him at once” (C. S. Lewis). Pleasure, of course, is not an end in itself. When the pleasure of a couple becomes self-enclosed and is not open to the new life that could result from it, it no longer corresponds to the nature of love.